At the moment it is not possible to delete a candidate card (test or regular) from a job.
We are working on adding an option to delete a candidate from a job.
In the meantime, you can try this workaround:
Create an custom company stage and name it "Archived" or whatever you like. Click on the 3 dot menu and remove the selection to send an email upon rejection.
Then drag the expired cards to that stage and reject each candidate.
The rejected candidate cards will disappear from the job dashboard and the candidates won't receive a rejection email since you removed the option to send that email upon rejection.